my milwaukee table saw is making a horrible grinding noise when it starts up, sounds like metal on metal

Diagnosis

The grinding noise occurring specifically during the startup phase of the Milwaukee M18 FUEL Table Saw (2736-20) is typically caused by mechanical interference between the rotating blade and the riving knife or the blade guard assembly. Because this saw uses a high-torque brushless motor, the initial surge of power can force a slightly misaligned component into the path of the blade, resulting in a harsh "metal-on-metal" screech. This often happens after the saw has been transported in a vehicle or if the blade was changed without properly resetting the riving knife position. To confirm this, you must perform a manual rotation test. If the blade catches or "clicks" at a specific point in its 360-degree rotation, you have a physical obstruction. If the noise only happens during the electronic ramp-up but the blade spins freely by hand, the issue may be internal to the motor housing or a loose mounting bolt on the arbor nut causing the blade to wobble (run-out) and strike the throat plate.

How to Fix It

Follow these precise steps to eliminate the interference and restore smooth operation:

1. Safety Isolation: Remove the M18 battery pack immediately. Never perform these adjustments with a power source connected, as the trigger could be accidentally engaged.
2. Manual Rotation Check: Slowly rotate the blade by hand for two full revolutions. Listen for the exact spot where the grinding occurs. Visually inspect the gap between the back of the blade and the riving knife.
3. Riving Knife Realignment: Locate the mounting bolt that secures the riving knife to the blade carriage. Loosen this bolt slightly using a wrench. Gently push the riving knife backward and ensure it is perfectly parallel to the blade. It should not touch the blade teeth at any point, but should maintain a consistent, narrow gap.
4. Guard Adjustment: Check the clear plastic blade guard. If it has been bumped, the mounting bracket may be bent. Ensure the guard is not sagging or leaning into the blade's path. If the guard is rubbing, loosen the adjustment knobs and shift the assembly outward.
5. Arbor Nut Tightening: Use the provided wrench to ensure the arbor nut is tightened securely. If the nut is loose, the blade will oscillate slightly during the high-RPM startup, causing it to strike the throat plate or the riving knife.
6. Throat Plate Inspection: Remove the throat plate (the insert around the blade) and check for accumulated sawdust or metal shavings that may have packed into the recess, pushing the plate upward into the blade path.

If That Didn't Work

• Check for Blade Warpage: If you are using a third-party blade or an old blade that has been dropped, the disc may be warped. Swap the blade for a brand-new, genuine Milwaukee blade. If the grinding disappears, the previous blade had a "wobble" that exceeded the clearance of the riving knife.
• Inspect the Motor Bearings: If the blade spins freely by hand but the grinding is internal (coming from the motor housing rather than the blade area), the front motor bearing may have failed or lost lubrication. This is rare for the 2736-20 but can happen if the tool was exposed to heavy moisture or extreme dust. This requires a professional teardown of the motor assembly.
• Verify Table Leveling: Ensure the saw is on a completely flat surface. If the chassis is twisted or leaning heavily, it can subtly shift the alignment of the internal carriage, causing the blade to rub against the internal housing of the saw.
• Clear Debris from the Lower Gear: Use compressed air to blow out the area around the arbor and the drive gear. A large piece of hardened resin or a metal screw caught in the gear teeth can cause a grinding sound during the initial torque surge.

Heads Up

• Blade Compatibility: Always ensure you are using a blade with a 5/8" arbor. Using a blade with a reducer ring that isn't seated perfectly can cause the blade to run off-center, leading to the exact grinding noise described.
• Riving Knife Maintenance: Never operate this saw without the riving knife installed. While it may seem like it causes interference, it is the only thing preventing "kickback," which can be catastrophic on a portable saw.
• Avoid Over-tightening: When adjusting the riving knife or guard, tighten bolts until they are snug. Over-torquing the bolts can strip the aluminum threads in the carriage, making it impossible to align the blade correctly.
• Battery Health: If the motor sounds like it is "struggling" or grinding electronically, ensure you are using a High Output (HO) battery. Low-capacity batteries can sometimes cause voltage drops during startup that affect the brushless controller's ramp-up sequence.